When you log in with your password and username a screen pops up that is titled "Enter Security Code."
1. Click the "I can't get my code" link in blue.
2. Click the "Skip this and stop asking me to enter codes" link in blue.
3. Click the "Turn off Security Codes button in blue. (it should log you in)
4. In the same browser go to url: https://www.facebook.com/settings.
5. Click the mobile phone icon on the left side of the screen.
6. Click remove on your old phone number.
7. Click "+ Add another mobile phone number" and follow the steps.
8. Once confirmed go to https://www.facebook.com/settings?tab=security.
9. Click edit on "login approval."
10. Checkmark the box and click save to re-enable the settings we disabled.
*UPDATE* Kimberly glad to see you solved your problem. However, a report is not necessary for Paul's case. (I guess you could file a report if you really want to.) That screenshot posted by Paul is new, It was not posted when I answered the question. Paul....your already logged in, it says it right on your photo ("log out"). Just skip to #4 on my list. If you can't perform step number 4 then use the link Kimberly gave you. ~Stay Safe, CyberGeek.